Reacción #93085

Ecuación de reacción

n-Butyllithium

diisopropylamine

(3S,4R)-1-(t-butyldimethylsilyl)-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-4-(2-oxoethyl)azetidin-2-one

Benzyl acetate

→

(3S,4R)-1-(t-butyldimethylsilyl)-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-4-(3-benzyloxycarbonyl-2-hydroxypropyl)azetidin-2-one

Disolventes

tetrahydrofuran

tetrahydrofuran

Condiciones de reacción

Tratamiento posterior

1. 1
   workup.STIRRINGthe resulting solution is stirred at -78° C. for 20 min
2. 2
   workup.STIRRINGThe reaction mixture is stirred at -78° C. an additional 15 min
3. 3
   Otroquenched by addition of saturated aqueous ammonium chloride solution
4. 4
   workup.ADDITIONEthyl acetate (50 ml) is added
5. 5
   Otrothe organic phase is separated
6. 6
   Lavadowashed with water (2×10 ml) and brine
7. 7
   Secadodried over magnesium sulfate
8. 8
   OtroRemoval of solvents in vacuo
9. 9
   Otrogives a white solid which
10. 10
    Otrois chromatographed on a short silica gel column (40% ether in petroleum ether)

Procedimiento

n-Butyllithium (1.81 mmol) is added by syringe to a solution of diisopropylamine (1.81 mmol) in 9 ml of freshly distilled tetrahydrofuran at -78° C. The resulting solution is stirred for 15 min at -78° C. Benzyl acetate (1.81 mmol) is then added dropwise by syringe and the resulting solution is stirred at -78° C. for 20 min. A solution of (3S,4R)-1-(t-butyldimethylsilyl)-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-4-(2-oxoethyl)azetidin-2-one (1.64 mmol) in 3 ml of anhydrous tetrahydrofuran is added slowly by syringe. The reaction mixture is stirred at -78° C. an additional 15 min and then quenched by addition of saturated aqueous ammonium chloride solution. Ethyl acetate (50 ml) is added and the organic phase is separated, washed with water (2×10 ml) and brine and dried over magnesium sulfate. Removal of solvents in vacuo gives a white solid which is chromatographed on a short silica gel column (40% ether in petroleum ether) to yield (3S,4R)-1-(t-butyldimethylsilyl)-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-4-(3-benzyloxycarbonyl-2-hydroxypropyl)azetidin-2-one. n.m.r. (CDCl3) δ7.32(s,5), δ5,1(s,2), δ4.0(m,3), δ2,4-3,8(m,4), δ2.0(m,2), δ1.25(overlapping d, 3), δ0.95(s,9), δ0.9(s,9), δ0.3(s,6), δ0.18(s,6).

Fuente